1. Field of the Invention
The present invention relates to a polishing pad, a polishing apparatus and a method for manufacturing a polishing pad.
2. Description of the Related Art
Polishing generally refers to a wear control for a preliminary coarse surface in a process of chemical mechanical polishing (CMP), which makes the slurry containing fine particles evenly dispersed on the upper surface of a polishing pad, and at the same time places a substrate to be polished against the polishing pad and then rubs the substrate to be polished repeatedly with a regular motion. The substrate to be polished may be objects such as a semiconductor, a storage medium substrate, an integrated circuit, an LCD flat-panel glass, an optical glass and a photoelectric panel. During the polishing process, a polishing pad must be used for polishing the substrate to be polished, and the quality of the polishing pad directly influences the polishing effect of the substrate to be polished.
FIG. 1 shows a schematic view of a polishing apparatus with a conventional polishing pad. The polishing apparatus 1 includes a lower base plate 11, a mounting 12, a substrate to be polished 13, an upper base plate 14, a polishing pad 15 and slurry 16. The lower base plate 11 is positioned opposite to the upper base plate 14. The mounting 12 is adhered to the lower base plate 11 through an adhesive layer (not shown) and is used for carrying and mounting the substrate to be polished 13. The polishing pad 15 is mounted on the upper base plate 14, and faces to the lower base plate 11 for polishing the substrate to be polished 13.
The operation mode of the polishing apparatus 1 is as follows. First, the substrate to be polished 13 is mounted on the mounting 12, and then both the upper and lower base plates 14 and 11 are rotated and the lower base plate 11 is simultaneously moved downward, such that the polishing pad 15 contacts the surface of the substrate to be polished 13, and a polishing operation for the substrate to be polished 13 may be performed by continuously supplementing the slurry 16 and using the effect of the polishing pad 15.
When polishing, the polishing pad 15 simultaneously withstands the pressure of the lower base plate 11 and upper base plate 14 from different ways. In order to avoid scraping the substrate to be polished 13, the polishing pad 15 usually comprises a polishing sheet and a base sheet. Depending on the substrate to be polished 13, the material of the polishing pad may be a non-woven fabric, an elastomer, or a mixture thereof. Most of the materials of the base sheet are a non-woven fabric as a main body and an elastomer filled therein. When the base sheet contains the non-woven fabric, it has better compression rate and recovery rate than that of the polishing sheet. Wherein, the compression rate can increase the adaptation between the polishing sheet and the substrate to be polished, and the recovery rate can increase the life span of the polishing pad.
However, in the manufacture of the non-woven fabric, control of the thickness uniformity is not easy, so using the base sheet with the non-woven fabric may often cause many problems due to the non-uniform thickness. For example, when the polishing pad withstands the pressure, the non-uniform thickness of the non-woven fabric causes the diversity of the density in different areas of the base sheet and yields the diversity of the compression rate. The area where the compression rate is smaller or the thickness is thicker may lead the friction between the polishing pad and the substrate to be polished to become bigger, and the polishing pad also wears faster. Due to the difference of the wear degree, a surface of the polishing pad becomes more uneven that causes unstable polishing surface removal rate of the substrate to be polished and poor flatness, and forms a defective product finally.
Therefore, a novel polishing pad in the field is needed to be developed to overcome the defect of the aforementioned non-uniform pressure of the non-woven fabric in the base sheet and to improve the polishing effect.